hi
I want t o drive a inductive load ( motor )with three relay ( left ,right and stop situations) that this relays are drived with uln2003an relay driver .mcu drives uln2003 .
all of the mcu and relays and supply transformer and other components are in one board and mcu is supplied with 5V with the lm7805 regulator and relays are supplied with the same transformer that provides the input of lm7805 after 4 1n4007 full bridge diodes . two capacitors are connected before(1000uf,25V) and aftre(1000uf,16V) the regulator lm7805 and one 100nF after 1000uf,16v capacitor. one coil pin of each relays are connected together to +12V and other coil pins are connected to output of uln2003 outpouts to obtain the GND to activation when mcu drives special relay .when the load connected to my board when relay actives the MCU reset and go to unknown routine that mcu have to resat .but when i disconnect the load , the circuit is fine without any problem.
please help me. other Contents in forum did not help me
For the voltage supply pin of your MCU ----- did you try adding bypass capacitors? Eg. try a 100 microfarad electrolytic across the MCU's voltage supply pin and ground. Could also put a 100 nF ceramic capacitor in parallel with the 100 microfarad too.
Are there any suggestions or answers?
Southpark:
For the voltage supply pin of your MCU ----- did you try adding bypass capacitors? Eg. try a 100 microfarad electrolytic across the MCU's voltage supply pin and ground. Could also put a 100 nF ceramic capacitor in parallel with the 100 microfarad too.
thanks. yes I have 1500uf ,16V and 100nF capacitors are connected in output of lm7805 that's the vcc and GND of MCU .
and I connected another 100nF capacitor to the nearest mcu's vcc and gnd pins .but the problem not be solved
this problem is occur when the relays start on/off . And is related to the relays contacts. It is not related to the activation of the relays coil , because the uln2003 has Freewheeling diodes in it.
This problem comes up on the forums here extremely frequently.
Switching impulses from the motor circuit are being coupled into the microcontroller circuitry. This is generally caused by untidy wiring.
Not only must you keep the motor wiring physically separate from all the low voltage and logic wiring, but on each side, all power supply and control wiring must be kept bundled with the corresponding ground returns such as to form no open loops.
Hi,
Can you post a schematic and a picture of your project please?
What are the relays you are controlling, spec/data?
What size, voltage/current is the motor?
Is the motor single or three phase?
What Arduino controller are you using?
Thanks.. Tom... 
yeganeh2019:
this problem is occur when the relays start on/off . And is related to the relays contacts. It is not related to the activation of the relays coil , because the uln2003 has Freewheeling diodes in it.
Those diodes only work if the "COM" pin on the ULN2003 is connected to the +ve supply used for the
relay coils - since you've not provided a circuit drawing we can't tell if that's wired up...
Rather than use words, its much clearer to draw the circuit diagram, and post that.
Its not entirely clear where the power for the MCU, relay and motor come from and relate to each other
from your description - a diagram is much clearer.
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